1. Field of the Invention
The invention provides nucleotide sequences from Coryneform bacteria coding for the ChrS protein and a process for the fermentative preparation of amino acids using bacteria in which the ChrS protein is attenuated.
2. Discussion of the Background
L-amino acids, in particular lysine, are used in human medicine and in the pharmaceutical industry, in the foodstuffs industry and very particularly in animal nutrition.
It is known that amino acids can be prepared by the fermentation of strains of Coryneform bacteria, in particular Corynebacterium glutamicum. Due to the great importance of this area, constant efforts are made to improve the methods of preparing amino acids. Process improvements may relate to fermentation technology such as stirring and supplying with oxygen, altering the composition of the nutrient media such as the sugar concentration during fermentation, working up to the product by, for example, ion exchange chromatography, or the altering the intrinsic performance of the microorganims.
To improve the performance properties of these microorganisms, methods of mutagenesis, selection and mutant choice are often applied. These methods yield strains that are resistant to antimetabolites or are auxotrophic for regulatory significant metabolites and which produce amino acids.
Methods of recombinant DNA engineering have also been used for Corynebacterium strains to improve L-amino acid production. Such methods involve amplifying individual amino acid biosynthesis genes and examining the effects on amino acid production.
However, there remains a critical need for improved methods of producing L-amino acids and thus for the provision of strains of bacteria producing higher amounts of L-amino acids. On a commercial or industrial scale even small improvements in the yield of L-amino acids, or the efficiency of their production, are economically significant. Prior to the present invention, it was not recognized that attenuation of the chrs gene encoding the ChrS histidine kinase would improve L-amino acid yields.
An object of the present invention is to provide novel measures for the improved production of L-amino acids or amino acid, where these amino acids include L-asparagine, L-threonine, L-serine, L-glutamate, L-glycine, L-alanine, L-cysteine, L-valine, L-methionine, L-isoleucine, L-leucine, L-tyrosine, L-phenylalanine, L-histidine, L-lysine, L-tryptophan, L-arginine and the salts (monohydrochloride or sulfate) thereof.
One object of the present invention is providing a novel process for improving the fermentative production of said L-amino acids, particularly L-lysine. Such a process includes enhanced bacteria, preferably enhanced Coryneform bacteria, which express attenuated amounts of a ChrS hisitine kinase or protein that has ChrS histidine kinase activity.
Thus, another object of the present invention is providing such a bacterium, which expresses an attenuated amount of a ChrS protein or gene products of the chrS gene.
Another object of the present invention is providing a bacterium, preferably a Coryneform bacterium, which expresses a polypeptide that has an attenuated ChrS histidine kinase activity.
Another object of the invention is to provide a nucleotide sequence encoding a polypeptide having the ChrS protein sequence. One embodiment of such a sequence is the nucleotide sequence of SEQ ID NO: 1.
A further object of the invention is a method of making ChrS protein or an isolated polypeptide having a ChrS histidine kinase activity, as well as use of such isolated polypeptides in the production of amino acids. One embodiment of such a polypeptide is the polypeptide having the amino acid sequence of SEQ ID NO: 2.
Other objects of the invention include methods of detecting nucleic acid sequences homologous to SEQ ID NO: 1, particularly nucleic acid sequences encoding polypeptides that have ChrS histidine kinase activity, and methods of making nucleic acids encoding such polypeptides.
The above objects highlight certain aspects of the invention. Additional objects, aspects and embodiments of the invention are found in the following detailed description of the invention.